The invention relates to a pressure regulating valve for a pulsating pressurized medium, wherein dampening of oscillations in the valve is desired.
Pressure regulating valves for pressurized systems with mainly static or more or less continuously varying pressure levels are commonly known. Such valves are not always suitable for use in systems exposed to a pulsating flow/pressure with varying frequencies. In cases where a valve is spring loaded towards an open or closed position, the spring-loaded component of the valve may start to oscillate. Simple valves of this type will merely comprise a valve seat and a spring-loaded spherical valve body. If, for instance, a spring-loaded spherical valve body or a piston in the valve should begin to oscillate, the function of the valve will be disturbed. Due to this, the entire system of which the valve is a part may be disturbed or caused to fail. Examples of other sources of disturbances that may cause the valve to oscillate are engine vibrations or other valves, causing pressure pulses when opening or closing.
One field of application for such a valve is for cooling of pistons in internal combustion engines. Under certain operating conditions, such as high load, it may be necessary to cool the pistons, which is usually done by spraying oil onto the underside of each piston. Such a solution is shown in EP-A1-0 460 299. A problem with this solution is that the oil pump supplying oil under pressure delivers a pulsating pressure, especially if a gear pump or duo-centric pump is used. Hence, the piston described in the above document may start to oscillate under certain conditions. This type of oscillation may cause increased valve wear and noise as well as interruptions of the flow of oil to the piston cooling arrangement.
The invention aims to minimize the oscillations in pressure regulating valves. This is achieved by means of a valve comprising a valve body provided with one or more inlet openings and one or more outlet openings for a pressurized medium, which inlet and outlet openings are connected by an internal cavity. A piston abuts a valve seat between said inlet and outlet openings and is axially slidable against a spring in said cavity in the valve body. The piston is spring loaded towards its closed position, whereby the valve opens when a predetermined pressure actuates the piston. Dampening of oscillations is achieved by providing the outlet side of the valve body with an opening having a surface smaller than the cross-section of the cavity. Said opening enables pressurized medium from the outlet openings to act on the piston in the same direction as the spring when the valve is opened.
By selecting a suitable diameter for the opening, oscillations of the pistons can be dampened to the frequency in the pressurized medium close to or equal to the natural resonance frequency of the system.
The spring biasing the piston towards its closed position is preferably enclosed by two more or less cup-shaped parts, whereby the piston makes up the first part and the second part constitutes a component closing the cavity. Said component consists of a washer, or a similar part, provided with an opening. The opening is in connection with the outlet side of the valve. It is, of course, possible to provide further embodiments of both the piston and the closing component.
The inlet and outlet openings of the valve are preferably made up from axially separated, radial openings between the outer periphery and the internal cavity of the valve body. The number and cross-section of the inlet and outlet openings can be selected so that a predetermined pressure drop across said openings is obtained. In a preferred embodiment, it is desired to keep the pressure drop across said openings as small as possible, in order to limit the pressure loss in the system. It is also possible to assemble the valve in a cavity having connections for pressurized medium inlets and outlets, to the corresponding inlet and outlet openings in the valve. The outer surface of the valve is suitably provided with circular grooves in connection with said inlet and outlet openings in the valve. The outer radial surfaces of the valve can also be provided with threaded sections for mounting the valve in said cavity.
If the valve is to be placed in the same flow conduit it is intended to regulate, the inlet opening may instead be shaped in an axial direction. It is for instance possible to shape the bore for the piston in the valve body as a through bore.
An advantage of the above invention is increased piston durability, reduced noise, and improved distribution of oil to the piston cooling arrangement.
The above advantages and other advantages, objects and features of the present invention will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings.